Wave meter



S. D. LAVOlE May 23, 1944.

WAVE METER Filed Sept. 24, 1941 3 Sheets-Sheet 1 INVEN'IOR 51mm D. \JwmE Atromazva May 23, 1944.

S. D. LAVOlE WAVE METER Filed Sept. 24, 1941 3 Sheets-Sheet 2 Anoansvs May 23, 1944. s. D. LAvolE 2,349,440

WAVE METER Filed Sept. 24, 1941 5 Sheets-Sheet 3 rm? luvem'oa STEPHEN D LAVO\E RTronn-nvs Patented May 23, 1944 REISSUED JUL i947 UNITED STATES PATENT OFFICE 13 Claims.

The present invention relates to wave meters, and more particularly to instruments for measuring the wave length or frequency of ultra-high frequency oscillations generated, for example, by an electronic tube oscillator.

There are, in general, two ways of measuring frequencies or wave lengths ifthe use of multivibrators and other auxiliary apparatus is disregarded. These two methods may be classified as (a) on line type,

(b) 0011 and condenser type.

The usual method of measuring the frequency of an oscillator with the transmission line type of wave meter is to couple the line to the oscillator and observe the change in the meter connected in the circuit of the oscillator as the line is shorted through maximum and minimum nodal points. A shorting bar is moved up and down the transmission line, shorting out successively adjacent points on the line. The impedance of the line is reflected back on the oscillator, and as the bar is moved back and forth through the maximum or minimum points the impedance of the oscillator outfit is changed. The meter is ordinarily placed in the grid circuit of the oscillator to indicate grid current which will vary in accordance with the changes in the impedance of the transmission line. This method will measure ultra-high frequencies, but not very accurately, for the reason that the transmission line represents distributed inductance and capacity so that the line responds not only to the basic frequency but also to multiples and submultiples thereof. The apparatus'does not lend itself to rapid measurement and is largeand cumbersome, requiring great care in making the determinations.

The coil and ,condenser type of wave meter, when designed and employed in the ordinary manner, is limited as tothe range of frequency measurement, and in general will give accurate results only up to a few hundred megacycles, because a meter of this type employs an open form of inductance and a condenser of the usual construction. It is apparent that in a construction of this kind considerable leakage of current through the condenser and coil is inevitable, so that a meter of this type is completely unreliable in the ultra-high frequency wave band, for example, between 300 and 700 megacycles.

The improved wave meter, which will be described presently, is of the coil-condenser type so completely modified as to increase the frequency range at which highly accurate results I are obtained. In the first place, the coil structure, as modified, has little or no resemblance to an ordinary wound coil, although providing the necessary inductive reactance. It has been found that coils of the ordinary type cannot be satisfactorily built at the present time which have a so-called ratio sufllciently'high to provide the requisite sharpness of the frequency resonance curve. Secondly, the necessary inductance is provided without any appreciable distributed capacity, and all of the capacity which controls the resonance frequency of the tuned circuit is lumped into a single element which may be readily and accurately adjusted.

The primary object of the present invention is to provide an accurate, compact and continuously variable wave meter for the ultra-high frequency spectrum.

Another object is to provide an ultra-high frequency 'wave meter which maintains its accuracy of measurement without further calibration over long periods of time and preferably over the entire operating life of the meter.

A further object is to provide an instrument of the type referred to, which is inexpensive, self-contained, portable, is shielded, and which has the minimum number of operating parts.

Another object is to provide an ultra-high frequency wave meter in which the frequencies to which the meter accurately responds may be readily adjusted over a relatively wide frequency range, and the measurement of frequency can be indicated directly in cycles per second or in wave length. 1

A still further object is to provide a wave meter which can accurately measure frequencies in a range above 300 megacycles, and the resonant circuits of the meter will not respond to the effects of multiple and sub-multiple frequencies.

In still another aspect the invention com prises an ultra-highfrequency meter in which the ratio of reactance to resistance Q is exceed ingly high in order to assure a sufllcient sharpness of the frequency resonance curve from which the frequency indications are derived.

. These objects are attained, in brief, by providing a meter which operates on the coil-conreferred to above, .but the structure has been I denser principle, employing maximum current indicationsias distinguished from null current), and in which the variations in frequency response are obtained by changing the eifects of a lumped capacity. The inductance of the resonant cir-p cult is provided without the use of an ordinary type of wound coil so that leakage between turns and also distributed capacity are avoided. The variable lumped capacitance of the improved meter resides between the rugged casing of the meter and the plunger which is given a reciprocatory movement of a positive and resettable character. I

Otherobjects and features will be apparent from a-reading of the following specification toof the arrows.

Figure 5 is a perspective view of the wave meter unit and associated gearing, the unit being broken away to show the internal parts.

Figure 6 is a fragmentary plan view of the anti-back lash gear forming part of the actuating mechanism.

Figure 7 is a section taken through a portion of the back lash gear to show the mechanism by which the back lash is eliminated.

Figure 8 is a small section taken along the line 8-8 in Figure 4, and showing a slightly modified optional structure.

Figure 9 is a diagrammatic layout of the circuit. Referring to the drawings, the ultra-high frequency wave meter embodying my invention is entirely housed except for the actuatin mechanism within a heavy approximately rectangular metal housing (Figures 3, 4 and 5), preferably a one-piece aluminum casting integrally closed onall sides except one side, and the open side being closed by a heavy metal cover plate 2 secured thereto by means of the screws 3, or in any other suitable manner. The casting I. also the cover plate 2, has a thickness of not less than 1%" so that the housing is of an extremely rugged I character, permitting no bends, warping or other relative displacement between the sides and the cover plate.

One of the sides is provided with a threaded opening 4 which is adapted toreceive the screw shank 5 of an input connector 6. This connector takes a general cylindrical shape and terminates at the end remote from the threaded portion 5 ina threaded collar 1, provided with a countersunk bore 8 and adapted to receive a, nut 9. The purpose of the nut will be explained presently. 'I'heinput connector is providedwith an axial bore which receives a metal rod l0, ex-

4 tending into a larger stub portion II on the interior of the housing I, and at the opposite end terminates in a metal terminal l2, provided with four quadrantal. sections which give a compression eiiectv to' a leading-in conductor Id. The rod I is insulated from the cylinder 6 bysuitable material, for example a plastic l of the polystyrene type. Material which is known on the market as Amphenol" may be used for this purpose. As the opposite side-of the housing I there is an opening which receives an insulating bushing l6, preferably of a plastic material, this bushing being adapted to receive a leading-out conductor I! which carries an, enlarged stub por tion I. The stub portions l and I8 are preferably in line with one another, extending toward the center of the housing, and are in inductive relation with respect to a variable lumped capacity, which will now be described.

The variable condenser is comprised essentially of a hollow cylindrical member IS, the interior of which is machined to dimension, terminating at the'bottom (Figures 3 and 4) in a flanged base 20 which is secured in any suitable manner to the lower side of the housing; The upper edge of the cylinder l9 isgiven a curvilinear shape in order to provide the variations in changes of capacitance when the parts of the condenser are moved with respect to one another. The movable portion of the'condenser is constituted-of a plunger 2| which is slidably received by a cylinder 22, the latter being flanged at 23 and secured to the cover plate 2 by the screws 24. There is a longitudinal groove 25 provided at one side of the cylinder and a screw 25, carrying a locknut 2| is such that when extended it will move into the circular opening formed by the cylinder IS in a snug fit, but without friction.

It is apparent that the plunger, also its groove 25, and the interior of the cylinder 22 are all machined to dimension and preferably polished.

It is desirable to coat the-plunger 2|, the interior of the cylinder i9 and-the two stubs ll, l8 with silver in order to provide a low resistance path for the high frequency energy, in which case the body of these elements may be formed of a higher resistance and cheaper metal, such as brass.

The plunger 2| is given its reciprocatory motion by means of a threaded rod 28, this rod extending practically the entire length of the plunger in order to assure stability of support. For this purpose the plunger-2| is provided with an internal bore which is threaded to receive the threads of the rod 28. The rod is shouldered at its upper end, as indicated at 29, the shouldered .portion being journalled in the cover plate 2 and extending-outside of the housing to serve as a shaft on which a large anti-back lash driving gear 30 and a pinion 3| are mounted The plunger 2| is provided at its upper end with a countersunk bore 32 which receives the lower end of a. compression spring 33, the latter bearing at its upper end against the under side of the cover plate 2. The purpose of the spring is to apply a constant pressure against the plunger 2| and thereby prevent any lost motion due to continued use.

It is apparent that a the gear 30 is rotated,

.in a manner which will be described presently,

the rod 28 will be likewise rotated, causing the plunger 2| to be moved either upwardly or downwardly depending on the direction in which the gear is rotated, and-thus to increase or decrease the distance d between the lower edge of the plunger and the nearest surface of the cylinder -|9.v The capacity of the wave meteris practically entirely concentrated in the space between the plunger 2| and the cylinder |9 so that variations of capacitance are obtained by moving the plunger with respect to the cylinder. The gear "is preferably constructed in such amanner as to eliminate all back lash, and the details of a preferred construction are shown in Figures 6 and 7.

' The gear 36 is peripherally split into two sections 34, 36, each section being provided with a rectangular opening 36 which is adapted to receive a compression spring 31. One of the sections, for example 34, is provided with a tab 38 which extends into the opening 36,- for example from left to right, as shown in Figure -6. The othersection fl is provided with a similar tab 39 positioned at the opposite side from the tab 36, and also extending into the opening 36. These tabs constitute oppofltely positioned pins for loeating the ends of the spring 31, the arrangement being such that the compressional effects of the spring serve to slide the gear section 84 with respect to the other section so that the teeth of the respective sections are slightly out of line with one. another. It is apparent that any looseness of fit between the teeth; 66 and teeth with which the gear meshes will be readily taken up by the relative movement between the gear sections 84, 36. The gear to is actuated by a pinion H which is journalled at the lower end in the cover plate 2, as indicated at it, and is provided with a hub 63 at the upper end, the hub portion being extended as a small diameter shaft M which is provided with attend-operated wheel 66. The shoulder between the shaft M and the hub 43 abutsa metal plate M which is separated from the cover plate iby means of the spacers 51. Thus by turning the hand wheel 66 it is possible to cause a 'reciprocatory motion of the plunger 2i through the pinion 8i, anti-back las gear 30, and the threaded rod 28. I

The pinion 3| engages a gear it which is suitably journalled in the plate t6, and a shaft 49 is extended from the gear it, this shait carrying at its outer end a dial M. 'The dial W is preferably divided into one hundred parts, of-whicheach tenth division has been indicated on the drawings ,The gear w is also adapted to mesh with a pinion M which is iournalled at the hub portion 62 (Figure-3) in the plate d6, this hub portion being'extended as a shaft 63 which carries a dial 6d, preferably marked off in divisions, zero to 50. The dials d, at are placed side-by- Side in the same planeand quite close together so that the indications of the inner portions of the dials may be simultaneously read through a glass window 56, secured in a rubber gasket 56 (Figure 4).

A consideration of the gearing in Figure 5 will show that as the hand wheel i6 is rotated the pinion M will drive the gear 39 at a step-down speed, and assuming that the number of teeth on the pinions M and Bi is equal, the gear 30 will cause the pinion 5i to rotate at the same speed as the pinion N and the hand wheel 65. Thus the dial it will turn at the same rate as the hand wheel 55. vHowever, the pinion ti, which has the same speed of rotation as the gear 36, drives the gear 68 at a relatively slow speed and the ratio between the number of teeth on the pinion and the gear is such that the dial 50, which is operated by the gear 448, is rotated at onefiftieth the speed of the dial 5B. Thus the gearing is such as to cause the number dial 50 to rotate fifty times slower than the counter dial-64 for a given type of device, and the construction of the gear 3i! is such as to prevent any back lash between this gear and either of its pinions 4|, 5|. when the hand wheel 46 is rotated the plunger 2i is reciprocated at a rate depending on the speed of rotation of the hand wheel and its direction of rotation, and the movements of the hand wheel are translated into exact reciprocatory movements at the plunger 2|. The indications at both dials may be readily seen through the window 55.

All of the parts of the wave meter described hereinbei'ore, including the gearing and with the exception of the wheel 45, are contained in a wooden case 51, preferably of oak and varnished on its exterior surface. The wooden case is extended about the four sides and the bottom but with the top open to receive a panel 58 of a suitable insulating material such as hard rubber, BakeliteQetc. The gasket 56 is preferably pro- -vided with a flange 69, which extends over and bears against the outer surface of the panel 58. This panel is held iniplace on a metal plate 60 by means of machine screws iii. The sides of the box which form the outer casing are held together by means of small angle iron pieces 62, one of which is shown at the upper left-hand corner in'Figure 4 as being secured to the metal plate 60 by a screw 63. The other leg of the angle iron member is fastened to the wooden side 64 by a wood screw 65. There is a layer of copper 66 extending over the inner surfaces of the wooden sides, the corner portions of each copper plate being inserted between the angle iron 62 and the wooden side, thus being maintalned rigidly in position. The purpose of the copper layer or sheet is electrically to shield the internal parts of the casing from any external fields, magnetic or electrostatic, so that the changes in electrical characteristics brought about by the movement of the plunger 2| are entirely free from deleterious efiects.

In addition to the use of a copper plate for shielding purposes, still another shield may be optionally employed about the aluminum casting within the wooden casing. As shown in Figure 8, the casting may be coated with paint or enamel of any suitable and well known type, which dries with a hard exterior surface but leaves a wet layer next to the aluminum casting. The purpose of the wet layer is to provide a conducting path of relatively high resistance around the aluminum casting between the input and output terminals, so that any leakage high frequency currents which tend to pass directly between the input terminal 6 and the output terminal ll around the metal casting will be dissipated as heat in the resistance path formed by the interior layer of the paint or enamel. In Figure 8'the paint or enamel layer has been generally designated 61, of which the. hard exterior layer is indicated at 68 and the wet interior layer at 69, these layers being separated by a dot and dash line.

The wooden side 66 nearest the input terminal 6 is provided with an opening iilwhich receives a circular cup-shaped member fil, made preferably of brass or aluminum, the "member being provided with a flange which bears against the outer surface of the wooden plate, as shown in Figure 4. The bottom of the cup-shaped member is provided with an opening 12 which is sufficiently large to snugly receive the threaded collar 1. The purpose of the member ii is to direct deleterious fields away from the input electrode l2 by reflection. The term nal 6 is provided with a shoulder 13, upon which the copper plate 66 and the bottom portion of the member ll rest. 'The nut 9 presses the copper plate 66 and the member H tightly grounded at 4 against the shoulder I3. The clamping eifect exerted by the nut 9 closes all of the crevices or cracks at this point through which otherwise ultra-high frequency currents may leak. The

arrangement is such that all of the high frequency elements of the instrument are indicated by single lines. Thus the copper layer 66 is shown as a vertical and horizontal line, grounded at I8, and

the input terminal 6 which contains the input.

stub II is shown as passing through the copper layer. The aluminum casting I is diagrammatically indicated as a rectangle, and the capacitance or condenser eifectexisting between thelower end of the plunger 2I and the cylinder I9 is represented by a variable condenser 11. The output stub is designatedJB, as in Figured, this stub being carried through the conductor IT to the grid I8 of a diode detector tube I9. The plate 89 of the tube is connected to the grid through a conductor 8i, and these two electrodes are connected through a resistor 82, by a conductor, to the control grid 84 of a high gain amplifier tube 85. The conductor 83 is preferably shielded throughout its length by a copper braid 86, and

the conductor is grounded as at 81 through a resistor 88. The cathode of the tube I9 comprises a filament 89, one leg of which is grounded as indicated at 99, the other leg 9| being connected to a corresponding filament terminal of th cascade-- connected amplifier tubes. The auxiliary grid 92 of the tube 85 is connected through a fixed condenser 93 to one leg of the filamentary cathode 94, this leg being grounded as indicated at 95. There is also a resistance connection indicated at 96 between the grid 92 and the B+ terminal of a battery, .which preferably is of the dry cell type.

The anode 91 of the tube 85 is connected through a conductor 98 and a resistor 99 to the 3-} side of the battery, the lower terminals of the resistors 96 and 99 being connected together as dicated at I99.

The amplifier 85 is capacitively coupled through a condenser IM to the control grid I92 -of a second high gain amplifier I93. The filamentary cathode is indicated at I94, having one leg I95. The control grid I92. is also grounded through a resistor I98. The auxiliary grid I9! is connected through a conductor I98 to the B+ side of the high potential battery. It will be noted that one leg of the cathodes. 89, 94 and I94 is connected through a common conductor I99 to the A+ side of a relatively high current dry cell battery. The plate II9 of the last amplifier tube I93 is connected through a conductor III to one end of a transformer primary I I-2, the other terminal of which is connected to the B+ side of the battery. IA direct current blocking condenser H3 is inserted in an extension of the line III, and a telephone jack I I4 of any suitable and well knowntype is connected tothe extension line, as indicatdi The secondary II 5 of the output transformer is shunted by an adjustable high resistance I I 5 rovided with a movable tap I II. This tapis connected through a-conductor II8 to one corner of a resistance bridge circuit shown at 9, the

opposite comer of which is connected through a conductor I29 to the lower terminal I2I of the transformer secondary. One of the intermediate of the bridge I I9, and the left-hand terminal I29 is connected through a conductor I 39 to the junction I3I of the resistor. 92 and the conductor 88.

Operation of the instrument and circuit Assume that the source of unknown ultra-high frequency ..is connected tothe conductor I4. These high frequency currents will pass tothe input stub II and induce currents. in the aluminum casting, also in the plung'erll .and'its associated cylinder I9, these currentsbeing vectorially 180 apart to constitute inductive and capacitative components: The inductive reactive component is of minor importance since the controlof the resonance of the circuit is vested almost entirely in the capacitative effect which is exercised between the lower surface of the, plunger 2| and the upper or nearer surface of the cylinder -I9. After passing through the resonance chamber comprising the aluminum casting. and the variable loaded capacity constituted of the plunger 2i. and thecylinder I9, the high frequency currents induce corresponding currents'in theoutput-stub I8 and are appliedto thecombined grid and plate of the detector'tube I9. At this point the oscillations are rectified and the direct current components are successively amcontact. with thefterminal J21 amplified currents are passed through -the bridge to the microamm'ete'r' I23. when the blade I29 makes contact with the 'terminal I39, the ammeter I23 will be connected di'rectly'to the detector I9, in which case the direct current components are not amplified but are received directly by themet'er.

" For making the test for frequency, assume that the apparatus as awhole has been properly calibrated. l;'he hand wheel 45 is rotated to cause the plunger H to recede from or approach the cylinder I9 until a maximum reading is observed at the microammeter I23. It is .obvious that under these conditions the movement of the mounted on the top cover of the casing, and in addition to the two indicators and the hand wheel there is a telephone'jack H4 and an-on-and oif switch I32" connected in the filament conductor I99, also a knob I33 for varying the. resistance II9,and finally a knob I34 which'is connected to the. switch blade I26.

It is apparent that the facefof the instrument ure ultra-high frequency such as in the range of contains only the minimum amount of apparatus, including the adjustment devices, so that the operation of the instrument as a whole is fairly simple. The casing 51 is sufllciently large to contain all of the necessary batteries, which are preferably of the dry cell type to increase their portability. The compactness of the instrument is clearly shown in Figure 2. The, batteries are conveniently placed in one corner of the casing, and the transformer contained in a shielded case I35 is secured to and well insulated from the top cover 60 of the casing. The variable resistor IIS and the switch I25 are also conveniently mounted on the top cover, and the latter in addition supports the resonance chamber 7. I. It is preferred to mount the detector 19 and the amplifiers 85, I03 on diflerent sides of the resonance chamber. In Figure 2 the detector is shown as being contained in a metal casing I36 secured to the front side of the chamber I, while the two amplifiers 85, I03 are contained in a metal casing It! on a different side of the container. All of the battery leads, indicated at I38, are taken from their respective batteries through heavily insulated cables to a removable adapter i139, which has prongs (not shown) making contact with sockets contained in a base member I40 secured to the amplifier casing. It is apparent that by moving the adapter I39 all battery connections are broken at the base MI].

From the foregoing it is evident that I have disclosed an improved wave meter which is adapted to measure either the frequency or wave length of high frequency oscillations which may be generated, for example, in a high frequency tube oscillator. The connections between the conductor it and the oscillator may be made in any suitable and well mown manner, such as by means of a loop dipole, capacity or a direct connection. Radiation from the stub II sets up a standing wave system in the resonator when the tuning adjustment exercised. at the wheel 45 and carried through the plunger 2i and the cylinder I9 is in tune. The chamber 9 may be considered as a variable impedance and having a high impedance at frequencies other than the resonance frequencies. It is apparent that the free end of the plunger 2i and the cylinder I9 may be shaped to present to each other an increment of area variable in accordance with any predetermined function as the portions are moved relatively. For example, assuming that the lower end of the plunger 2| is fiat, the cylinder I9 could be given a contour at the edge which would cause a straight-line function between the instantaneous position of the plunger 2| and either frequency or wave length of the currents to which the chamber has been attuned. Thus the meter I23 may be calibrated in either frequency or wave length, depending on the shape of the edge surface at the cylinder I 9.

It will be further noted that, due to the complete absence of back lash at the gear formed of the sections 86, 85 and the compression efiect exeroised at the spring 33, a direct and positive relation is established between the instantaneous positions of the plunger 2i and the indications of that position shown by the dials 50, 54. Thus the improved instrument has a high degree of resettability so that the wave meter could be used for many years and still operate according to the calibration curve which had been determined by the manufacturer. This consideration is very important in connection with meters which meas- 300 to 700 megacycles.

The concentric arrangement of the plunger 2| and the cylinder I8 is such that a movement of the plunger affects solely the capacitative element of the resonant circuit because the mutual inductance between the central cylindrical portion 22 and the outer casting I remains substantially constant regardless of the position of the phmger. Consequently, the movements of the plunger 2| introduce only a oapacitative change in the characteristics of the resonant circuit, and this capacitance is loaded at one general point free from any deleterious magnetic or electrostatic eifects and controllable solely by the operation of the hand wheel 45.

While I have described the improved instrument as being adapted to measure the frequency or wave length of ultra-high frequency oscillations, it will be understood that the instrument, if desired, may be designed to measure frequencies in the lower frequency ranges. Proper choice of the pitch of the threaded control shaft 28, size of the gears lit, di, 68, 5|, dimensionsof the chamber I and cover plate a of the variable capacity elements 2!, I9 and the shape of the curve of the cylindrical element it and the movement of the variable capacity plunger 2| may allIbe so designed that the range of frequencies over which the instrument will accurately respond may be considerably changed. However, the improved instrument has an important advantage over other instruments, particularly in the ultra-high frequency range, of responding to only one frequency as determined by the maximum reading at the meter I23, and positively will not respond toany harmonic or sub-multiple-frequency, as is the case in instruments operable on the Lechcr wire principle. The instrument operates on the principle of maximum current reading rather than null current reading, and thus introduces additional accuracy into the determinations.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims an the invention.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A wave meter for measuring ultra-high frequencies comprising an electrically resonant chamber including a closed metal container, a first metal portion secured to and projecting inwardly from one Wall of said container, a second metal portion secured to and projecting inwardly from the wall approximatelyppposite said first metal portion to form an electrical capacity therebetween, the free ends of said metal portions being shaped to present to each other an increment'of area variable in accordance with a predetermined function as said portions are moved relatively, means for changing the resonance frequency of the resonant circuit thus formed by said container and said portions comprising means for moving the free ends of said portions relatively toward and away from one another, and coupling m eans positioned within said container for applying unknown frequencies to the resonant chamber and for withdrawing the oscillations from the resonant chamber for measuring purposes, said coupling means includinginput and output electrodes of rod-like configuration and arranged coaxially in line with one another on opposite sides of said metal portions.

2. A wave meter comprising an ultra-high fretainer and concentric with said tubular member to form therewith an electrical capacity, the extended end of one of said members being shaped to present a. variable increment of area'to the otherof said members in accordance with a predetermined function as one is moved toward the other, means for changing the resonance frequency of the resonant circuit thus formed by brated in frequency the resonance frequency of the resonant circuit to said resonant circuit, means comprising an output stub for withdrawing oscillations from said resonant circuit, and means for measuring the withdrawn current in terms of frequency,

said last-mentioned means comprising a rectifier and an amplifier together with an ammeter caliin the output circuit of the amplifier. A, 5 v

5. A wave meter comprising an ultra-high frequency resonant circuit formed of-a closed metal said container and said members comprising means for moving the free end of one of said members toward and awayfrom the other of said members, means including an input electrode for applying oscillations of unknown frequency to said'resonant circuit, and means ineluding an output electrode for withdrawing oscillations from said circuit and applying thewithdrawal oscillations to a frequency indicating device, said input and output electrodes being presented endwise and in coaxial alignment to the opposite sides of said tubular and cylindrical members.

3. A wave meter'comprising an ultra-high frequency resonant circuit formed, of a closed metal 1 container, a tubular metal member secured to and projecting inwardly from one wall of said the resonance frequency of the resonant circuit thus formed by said container'and said members comprising means for moving the free ends of said members relatively toward and away from each other, means comprising an input stub electrode which passes through said metal container for applying oscillations of unknown frequency to said resonant circuit, means comprising an output stub for withdrawing oscillations from said resonant circuit, and means for measuring the withdrawn current in terms of frequency.

4. A wave meter comprising an ultra-highfrequency resonantcircuit formed ofa closed metal container, a tubular metal member secured to and projecting inwardly from one wall of said container, a first cylindrical metal member secured to and projecting inwardly from the approximately opposite wall of said container, and concentric with said tubular member to 'forrn therewith an electrical capacity, a second cylindrical metal member secured to one of said other members and concentric therewith to form with the other ofsaid members a fixed lumped electrical capacity, the extended ends of said two first-mentioned members being shaped to'present to each other an increment of area variable in accordance with a predetermined function as they are moved relatively, means for changing I nant circuit thus formed by said container and container, a tubular metal member-secured to and projecting inwardly from one wall of said container, a cylindrical metal member secured to and projecting inwardly from the approximatelyopposite wallof said container and concentric with said tubular member to form therewith an electrical capacity, the extended end of one of said members being shaped to terminate in [a plane oblique to the common axis of said members, means for changing the resonance frequency of the resonant circuit thus formed by said container and said members comprising means for moving the free end of one of said members toward and away from the other of said members, and coupling means positioned. within said container for connecting said resoof said members.

6. A wave meter comprising an ultra-high frequency resonant circuit formed of the following elements in combination: a closed metal container, a tubular metal member secured to and projecting inwardly from one wall of said container,-a cylindrical metal member secured to the approximately opposite wall concentrically with said tubular member. and projecting into but out of physical contact therewith to form an electrical capacity therebetween, means for changing the resonance frequency of the resosaid concentric members comprising mechanical means relatively moving said members to move said cylindrical member into and out of said a tubular member, and means including stub electrodes which .extend from opposite sides of the be measured by a frequency indicating apparatus.

7. A waye meter comprising an ultra-high frequency resonant circuit formed of the following elements, in combination: a closed metal container, a tubular metal member secured to and projecting inwardly from one wall of said container, a cylindrical metal member secured to the approximately opposite wall concentric with said tubular member and projecting into. but out of physical contact therewithto form an electrical capacity therebetween, a threaded shaft meshed into a threaded hole along the longitudinal axis of said cylindrical member, control means accessible from the exterior of 'said container for rotating said shaft to move said cylindrical member into and out of said tubular member to vary'the resonance frequency of the resonator formed by said container and said concentric members,- means including an input electrode for applying to said resonant circuit oscillations of unknown frequency, and means including an output electrode for withdrawing oscillations from said circuit and applying the withdrawn oscillations to a frequency determining apparatus, said electrodes being presented coaxially in line with one another to said metal members from opposite sides of the container.

8. In a self-shielded ultra-high frequency wave meter, in combination, a closed metal housing and a resonant circuit contained within the housing, said housing forming part of the resonant'circuit, means for adjusting the resonance of said circuit, means including an input electrode for applying to said circuit frequencies to bemeasured, and means including an output electrode for withdrawing oscillations from said circuit and for applying the withdrawn oscillations to frequency indicating apparatus, said electrodes being presented to said resonant circuit coaxially in line with one another from opposite 'sides of the housing.

9. In combination, an ultra-high frequency wave meter comprising a metal housing completely surrounding an adjustable condenser, said housing forming with said condenser a resonant circuit, means including an input electrode for applying oscillations of unknown frequency to the resonant circuit, and means including an output electrode for withdrawing oscillations from the circuit and applying the same 'to frequency indicating apparatus, said electrodes being presented to said resonant circuit coaxially in line with one another from opposite sides of the housing said housing acting as a complete shield for the resonant circuit of which it forms a part.

10. A wave meter comprising a casing containing a circuit resonant to the frequency to be measured, said circuit including an inductance and a lumped variable capacity, input and output leads for said circuit, said input lead being connected to the source of unknown frequency and the output lead being connected to frequency measuring apparatus, said lumped capacity comprising movable and stationary metal elements, one element extending from one side of the casing and the other element extending from the opposite side, the electrical interaction of said elements and the casing constituting the inductance portion of the resonant circuit, said in- .put and output leads extending coaxially in line with one another into said casing from'opposite sides of said movable and stationary elements.

11. A wave meter comprising an ultra-high frequency resonant circuit, said circuit including a metal container, a first metal portion secured to and projecting inwardly from one wall of said container, a second metal portion secured to and projecting inwardly from the wall approximately opl $ite said first metal portion to form an electrical capacity therebetween, the electrical interaction of said metal portions and the casing con-' a closed metal container, a first metal portion secured to one wall of said container and having a free end projecting inwardly therefrom, a second metal portion secured to the wall approximately opposite said first metal portion to form an electrical capacity therebetween and having a free end projecting inwardly therefrom, means for changing the resonance frequency of the resonant circuit thus formed by said container and said portions comprising means for moving the free ends of said portions relatively toward and away from one another, a stub input electrode for applying to the container and metal portions an alternating current voltage of unknown frequency and an output stub electrode for withdrawing from the container and metal portions output current which is supplied to frequency indicating apparatus, and a plate electrode positioned in the region of the input electrode and electrically insulated therefrom for reflecting undesired oscillations away from the input electrode.

13. A wave meter comprising, in combination, a closed metal container, a first metal portion secured to one wall of said container and having a free end projecting inwardly therefrom, a second metal portion secured to the wall approximately opposite said first metal portionto form an electrical capacity therebetween and having a free end projecting inwardly therefrom, means for changing the resonance frequency of the resonant circuit thus formed by said container and said portions comprising means for moving the free ends of said portions relatively toward and away from one another, a stub input electrode for applying to the container and metal portions an alternating current voltage of unknown frequency and an output stub electrode for withdrawing from the container and metal portions output current which is supplied to frequency indicating apparatus, a wooden casing surrounding said metal container and metal portions, and a metal plate electrode positioned adjacent said input stub electrode and electrically insulated therefrom for reflecting undesired oscillations from the input electrode, said plate electrode being fitted within a depression formed in the wooden casing.

STEPHEN D. LAVOIE. 

